P_2.1.1 mature_wood

Utilization of the Mechanical Potential of Large Dimensioned Timber for System Structures in Engineering Timber Constructions

Strong wood is defined as spruce having a breast height diameter > 50 cm. Forests with a predominant share in coniferous wood and of secondary economic interest – as is usually the case with privately-owned small woods and woods growing on steep slopes – partly show an excessive share in strong wood.

Austria is, in fact, one of the countries with such a small-structured pattern of owned woodland, and it has lots of steep slopes. Also, Austria is characterised by a high concentration of saw mills equipped with high-performance chipping lines. However, their open face technology is, as a rule, optimised when it comes to the cutting of weak wood. Large dimensiones logs revealing a mean diamter of 40 cm and above can thus only under certain conditions be subjected to a high-performance open face. Contrary to this, from a forestry point of view and taking into account the principle of the “unit-mass law“, the harvest of strong is sought after. From a technical point of view, timber obtained from older logs and thus having a more mature cell structure, is to be preferred. It is a well-known factor that the mechanical properties, i.e. density, tensile, compression and bending strengths as well as the elasticity modules – all of these essential specific parameters for constructive application – are, on average, increased the further away they are from the core or the adult trunk area (see Project XXL-Wood: Teischinger, Patzelt 2006); however, at the same time, through, precisely these increased diffusion, these properties seem less suitable for use.

It is the objective of this project to examine the use of strong wood for application in high-performance, rod-like engineered products while considering the sorting and homogenisation effect of specifically composed system structures.

Based on the knowledge of the mechanical potential of the basic material – the sawn timber and finger joints – at varying qualities, the aim is to assess the performance potential for an application of strong wood in rod-like structures by means of models that take into account stochastic principles. Additionally, when using components of the same population, rod-like products are built up and are tested as to bending, traction and compression parallel to the grain. In this way, the mechanical performance potential for a validation of the stochastic models can be experimentally determined.